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Compound Interest Calculator

See how a deposit plus monthly savings grows year by year with monthly or yearly compounding, with the rule of 72 and optional South Korea 15.4% interest tax.

Inputs

Initial deposit

Monthly contribution

Assumed at the start of each month. 0 if none

Annual return (%)

Period (years)

1–100 years

Deduct Korean interest tax (15.4%)

Target amount (optional)

Shows how long it takes to get there

After 10 years, before tax94,434,739

Total contributed: 70,000,000
Interest (before tax): 24,434,739
Return (on contributions): 34.9%

ContributionsInterest1 bar = 1 year

Rule of 72 At 5% a year, your initial deposit doubles in about 14.4 years (exactly 13.9 years).

Show year-by-year amounts

Year	Contributed	Interest	Balance
1 year	16,000,000	676,628	16,676,628
2 years	22,000,000	1,694,844	23,694,844
3 years	28,000,000	3,072,126	31,072,126
4 years	34,000,000	4,826,844	38,826,844
5 years	40,000,000	6,978,308	46,978,308
6 years	46,000,000	9,546,816	55,546,816
7 years	52,000,000	12,553,705	64,553,705
8 years	58,000,000	16,021,404	74,021,404
9 years	64,000,000	19,973,488	83,973,488
10 years	70,000,000	24,434,739	94,434,739

Monthly compounding adds interest to the balance every month; annual compounding adds the year’s interest at year end. With tax on, 15.4% (Korea’s 14% interest income tax + 1.4% local income tax) is deducted once from all accumulated interest at the end. Real products differ in fees, tax treatment and rate changes, so results may vary. For bank deposit and savings interest at maturity, use Deposit and savings interest calculator. This is not investment advice.

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How to use

Everything you enter is processed only in this browser.

Enter the initial deposit and monthly contribution
Set the annual return, period and compounding frequency
Check the yearly growth and how long it takes to reach your target

How it works and good to know

Monthly contributions are assumed to be made at the start of each month. Monthly compounding adds interest to the balance at the end of each month; annual compounding accumulates simple interest during the year and adds it at year end. Turning on tax deducts Korea’s 15.4% interest income tax once, at the end, from all accumulated interest. The Rule of 72 (72 ÷ annual return) is shown alongside the exact doubling time. The period is 1–100 years and the return 0–100%. Fees and rate changes aren’t reflected, and this isn’t investment advice.

Compound Interest Calculator

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